It is part of the classification of rings and belts that can be mined. "Pristine" is the richest (means it only has been exploited a little or not at all). At the other end of the spectrum, you have "depleted", and several others in between, like "rich", "common", etc.
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I've seen plenty of brown dwarves with rings, better still are T-Tauri stars with rings. If you want to find a pristine ring just venture outside of the human occupied areas and all rings will be pristine.
Tor.....Hold on.......Tor.......Wait a bit.....TOR will you stop fecking firing.......Ok......Tor I know a therapist that can help you....... My Cmdr also has small feet